diff --git a/docs/shared-mutable-state-and-concurrency.md b/docs/shared-mutable-state-and-concurrency.md
index 1a3c406472..96f6fdf129 100644
--- a/docs/shared-mutable-state-and-concurrency.md
+++ b/docs/shared-mutable-state-and-concurrency.md
@@ -187,7 +187,7 @@ suspend fun massiveRun(action: suspend () -> Unit) {
 }
 
 //sampleStart
-var counter = AtomicInteger()
+val counter = AtomicInteger()
 
 fun main() = runBlocking {
     withContext(Dispatchers.Default) {
diff --git a/kotlinx-coroutines-core/jvm/test/guide/example-sync-03.kt b/kotlinx-coroutines-core/jvm/test/guide/example-sync-03.kt
index 6c34149c93..8153c026b4 100644
--- a/kotlinx-coroutines-core/jvm/test/guide/example-sync-03.kt
+++ b/kotlinx-coroutines-core/jvm/test/guide/example-sync-03.kt
@@ -24,7 +24,7 @@ suspend fun massiveRun(action: suspend () -> Unit) {
     println("Completed ${n * k} actions in $time ms")    
 }
 
-var counter = AtomicInteger()
+val counter = AtomicInteger()
 
 fun main() = runBlocking {
     withContext(Dispatchers.Default) {